The objective of this investigation is the development of a rapid non-isotopic method for the measurement of therapeutic protease inhibitors in the serum of patients infected with HIV. Dosing of protease inhibitors is based on the level of drug necessary to inhibit HIV. However, achievement of therapeutic levels is influenced by multiple, often uncontrollable, factors. As a result, the peak, trough and steady state levels have considerable individual variability. For some patients trough levels may be sub-therapeutic and for others, the peak is so high as to cause toxic side effects. It has also been determined that HIV is able to mutate and evolve resistance to protease inhibitors, particularly when the level of the enzyme inhibitors in the serum is sub-therapeutic. For these reasons, clinicians have expressed the need for a rapid and inexpensive test; it should be performed close to the point of care and able to determine the serum level of protease inhibitors. However, the only available tests are based on drug extraction from the serum with organic solvents followed by measurement by methods based on high performance liquid chromatography (HPLC). These HPLC methods are available at a relatively high cost at highly specialized laboratories principle. The HIV protease degrades a specific substrate, which release a non-isotopic measurable signal. In the presence of diluted patient serum, the activity of the enzyme is inhibited and the signal is reduced proportional to the concentration of inhibitor. Experiments are designed to obtain preliminary data for the development of a practical and robust test comparable in accuracy with those obtained by HPLC methodology. PROPOSED COMMERCIAL APPLICATION: NOT AVAILABLE